Data Acquisition Acceleration In Magnetic Resonance Angiography Applications Using Magnetization-Prepared Simultaneous Multi-Slice Acquisition

ABSTRACT

A method for producing an image representative of the vasculature of a subject using a MRI system includes the acquisition of a signal indicative of a subject&#39; cardiac phase. During each heartbeat of the subject, image slices of a volume covering a region of interest (ROI) within the subject are acquired by applying a volume-selective venous suppression pulse to suppress (a) venous signal for an upper slice in the ROI; (b) venous signal for slices that are upstream for venous flow in the ROI; and (c) background signal from the upstream slices. Next, a slice-selective background suppression pulse is applied to suppress background signal of the upper slice. Following a quiescent time interval, a spectrally selective fat suppression pulse is applied to the entire volume to attenuate signal from background fat signal. Then, a simultaneous multi-slice acquisition of the upper slice and the upstream slices is performed.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of U.S. Ser. No. 15/332,107 filed onOct. 24, 2016, the contents of which are incorporated by reference.

TECHNOLOGY FIELD

The present invention relates generally to methods, systems, andapparatuses for accelerating data acquisition in magnetic resonanceangiography applications using magnetization-prepared simultaneousmulti-slice acquisition.

BACKGROUND

Non contrast-enhanced magnetic resonance angiography (NE-MRA) is usefulin the evaluation of vascular pathologies, especially in patients withimpaired renal function. Most of the NE-MRA techniques rely on bloodflow into a sequential series of 20 slices or 30 blocks until the entirevascular territory of interest is imaged. This process of sequentialacquisition can potentially result in long scan times for the patient.

Many techniques exist to accelerate image acquisition to thereby reducepatient examination time. These exploit different aspects inherent in MRdata. For instance, the use of phased-array coils provides additionalinformation encoded in spatially varying sensitivity of the individualcoil elements; this can be used to extract more information from thesame data. More advanced techniques have been developed thatsimultaneously excite multiple spatially-separated slices, and then usecoil sensitivities to extract the information in each individual slice;these are collectively called simultaneous multi-slice (SMS) imaging.

In addition to maximizing the signal from blood vessels, NE-MRA requiresthe minimization of signal from other tissues (e.g., background muscles,fat, etc.) so as to improve conspicuity of vessels. Often,radiofrequency suppression pulses are used for this purpose; thesepulses suppress the magnetization from the background tissues, thusminimizing the signal emanating from them.

As mentioned above, conventional NE-MRA techniques rely on inflow ofblood to generate the required contrast—accentuation of arteries andsuppression of veins and background. One such NE-MRA technique is calledquiescent interval slice-selective (QISS). In this approach, threedifferent preparation pulses are used to suppress background tissue,venous signal, and fat signal. Quiescent interval (QI) is a timeinterval during which no activity takes place so as to permit inflow ofsufficient unsuppressed blood into the slice of interest. The MR signalacquired after the QI time represents primarily arterial signal. Theprocess is then repeated for all slices, until the entire vascularanatomy of interest is covered. The series of slices are then stackedtogether to depict the vascular tree.

The use of SMS is attractive for accelerating data acquisition of NE-MRAtechniques such as QISS; however, it requires redesign of spatial andtemporal application of magnetization preparation pulses to accomplishsimilar images in less time. Thus, it is desired to provide techniquesfor combining NE-MRA with SMS and magnetization preparation pulses in amanner that minimizes the overall acquisition time.

SUMMARY

Embodiments of the present invention address and overcome one or more ofthe above shortcomings and drawbacks, by providing methods, systems, andapparatuses which accelerate data acquisition in magnetic resonanceapplications using magnetization prepared simultaneous multi-sliceacquisition. Briefly, the techniques described herein combine NE-MRAwith SMS using suppression pulses that are modified such that the venoussuppression pulse not only suppresses the venous signal for eachacquired slice, but the background for the slice that is upstream forvenous flow is also suppressed.

According to some embodiments, a method for using magnetic resonanceangiography to produce an image representative of the vasculature of asubject with a magnetic resonance imaging (MRI) system includesacquiring a signal indicative of a cardiac phase of the subject. Duringeach heartbeat of the subject (e.g., following a user-selected timedelay after the R-wave of each heartbeat), image slices of a volumecovering a region of interest within the subject are acquired using anacquisition process. During this process, a volume-selective venoussuppression pulse is applied to suppress (a) venous signal for an upperslice in the region of interest; (b) venous signal for one or moreslices that are upstream for venous flow in the region of interest; and(c) background signal from the upstream slices. The volume-selectivevenous suppression pulse may include, for example, a tracking saturationpulse applied downstream to the upper slice and the upstream slices.Next, a slice-selective background suppression pulse is applied tosuppress background signal of the upper slice. The slice-selectivebackground suppression pulse may apply, for example, a 90 degree or 180degree flip angle to the upper slice. Following a quiescent timeinterval, a spectrally selective fat suppression pulse is applied to theentire volume to attenuate signal from background fat signal. Once thepreparation pulses have been applied, a simultaneous multi-sliceacquisition of the upper slice and the upstream slices is performed.This simultaneous multi-slice acquisition may be performed using asingle-shot pulse sequence. For example, in some embodiments, thesingle-shot pulse sequence is a balanced steady-state free precessionpulse sequence or spoiled gradient echo pulse sequence.

In some embodiments of the aforementioned method, the spectrallyselective fat suppression pulse is a 90 degree RF pulse which rotatesmagnetizations in fat tissue of the entire volume into the x-y plane ofthe subject. In other embodiments, the spectrally selective fatsuppression pulse is a 180 degree RF pulse which completely invertslongitudinal magnetization of fat in the entire volume. The method maythen further include waiting a predetermined inversion time prior toperforming the simultaneous multi-slice acquisition of the upper sliceand the one or more upstream slices. This predetermined inversion timemay be selected such that longitudinal magnetization of fat in the upperslice and the upstream slices recovers through a zero point whenacquiring k-space data during the simultaneous multi-slice acquisition.

According to other embodiments, a second method for using magneticresonance angiography to produce an image representative of thevasculature of a subject with a MRI system includes acquiring a signalindicative of a cardiac phase of the subject. During each heartbeat ofthe subject, image slices of a volume covering a region of interestwithin the subject are acquired using an acquisition process. Duringthis process, for each of the plurality of image slices, the followingpulses are applied: (a) a volume-selective venous suppression pulse tosuppress venous signal downstream from venous flow into the image sliceand (b) a slice-selective background suppression pulse to suppressbackground signal of the image slice. Additionally, following aquiescent time interval, a spectrally selective fat suppression pulse isapplied to attenuate signal from background fat signal in the entirevolume. Then, a simultaneous multi-slice acquisition of the plurality ofimage slices may be performed. Various features, enhancements, and othermodifications may be made to this second method which are similar tothose described above with respect to the other method for usingmagnetic resonance angiography to produce an image representative of thevasculature of a subject discussed above.

According to another aspect of the present invention, a system for usingmagnetic resonance angiography to produce an image representative of thevasculature of a subject includes an electrocardiogram device, animaging device, and a central control computer. The electrocardiogramdevice is configured to acquire a signal indicative of a cardiac phaseof the subject. The imaging device includes a plurality of coils whichare used to apply a preparation pulse sequence to a volume during eachheartbeat of the subject. This preparation pulse sequence comprises avolume-selective venous suppression pulse that suppresses (a) venoussignal from an upper slice in a region of interest, (b) venous signalfrom one or more upstream slices that are upstream for venous flow inthe region of interest, and (c) background signal from the one or moreupstream slices. The sequence further includes a slice-selectivebackground suppression pulse that suppresses background signal of theupper slice, and a spectrally selective fat suppression pulse applied tothe volume to attenuate signal from background fat signal. The imagingdevice is further configured to perform a simultaneous multi-sliceacquisition of the upper slice and the one or more upstream slicesfollowing each preparation pulse sequence to update a k-space datasetcovering the region of interest. The central control computer unit isconfigured to apply a reconstruction process to the k-space dataset togenerate one or more images.

Additional features and advantages of the invention will be madeapparent from the following detailed description of illustrativeembodiments that proceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other aspects of the present invention are bestunderstood from the following detailed description when read inconnection with the accompanying drawings. For the purpose ofillustrating the invention, there is shown in the drawings embodimentsthat are presently preferred, it being understood, however, that theinvention is not limited to the specific instrumentalities disclosed.Included in the drawings are the following Figures:

FIG. 1 shows a system for ordering acquisition of frequency domaincomponents representing magnetic resonance imaging (MRI) data forstorage in a k-space storage array, as used by some embodiments of thepresent invention;

FIG. 2A provides an illustration of an image acquisition sequence 200that may be implemented on the system 100, according to some of thetechniques described herein;

FIG. 2B shows the spatial location of the pulses shown in FIG. 2A in aschematic of vascular anatomy;

FIG. 3A provides an illustration of an alternative image acquisitionsequence 300, according to some embodiments;

FIG. 3B shows the spatial location of the pulses shown in FIG. 3A in aschematic of vascular anatomy;

FIG. 4 shows a process 400 for using magnetic resonance angiography toproduce an image representative of the vasculature of a subject,according to some embodiments of the present invention; and

FIG. 5 illustrates an exemplary computing environment 500 within whichembodiments of the invention may be implemented.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The following disclosure describes the present invention according toseveral embodiments directed at methods, systems, and apparatusesrelated to accelerating data acquisition in magnetic resonanceangiography applications. More specifically, the techniques describedherein combine SMS imaging with magnetization preparation to achievescan time reduction in magnetic resonance angiography (MRA) applicationsby a factor of N, where N is the number of slices that are excitedsimultaneously. As described in more detail below, this is achieved, inpart, by using a preparatory pulse sequence comprising a venoussuppression pulse that not only suppresses the venous signal for eachacquired slice, but also the background for the slice that is upstreamfor venous flow.

FIG. 1 shows a system 100 for ordering acquisition of frequency domaincomponents representing magnetic resonance imaging (MRI) data forstorage in a k-space storage array, as used by some embodiments of thepresent invention. In system 100, magnetic coils 12 create a static basemagnetic field in the body of patient 11 to be imaged and positioned ona table. Within the magnet system are gradient coils 14 for producingposition dependent magnetic field gradients superimposed on the staticmagnetic field. Gradient coils 14, in response to gradient signalssupplied thereto by a gradient and shim coil control module 16, produceposition dependent and shimmed magnetic field gradients in threeorthogonal directions and generates magnetic field pulse sequences. Theshimmed gradients compensate for inhomogeneity and variability in an MRIdevice magnetic field resulting from patient anatomical variation andother sources. The magnetic field gradients include a slice-selectiongradient magnetic field, a phase-encoding gradient magnetic field and areadout gradient magnetic field that are applied to patient 11.

Further radio frequency (RF) module 20 provides RF pulse signals to RFcoil 18, which in response produces magnetic field pulses which rotatethe spins of the protons in the imaged body of the patient 11 by ninetydegrees or by one hundred and eighty degrees for so-called “spin echo”imaging, or by angles less than or equal to 90 degrees for so-called“gradient echo” imaging. Gradient and shim coil control module 16 inconjunction with RF module 20, as directed by central control unit 26,control slice-selection, phase-encoding, readout gradient magneticfields, radio frequency transmission, and magnetic resonance signaldetection, to acquire magnetic resonance signals representing planarslices of patient 11.

In response to applied RF pulse signals, the RF coil 18 receivesmagnetic resonance signals, i.e., signals from the excited protonswithin the body as they return to an equilibrium position established bythe static and gradient magnetic fields. The magnetic resonance signalsare detected and processed by a detector within RF module 20 and k-spacecomponent processor unit 34 to provide a magnetic resonance dataset toan image data processor for processing into an image. In someembodiments, the image data processor is located in central control unit26. However, in other embodiments such as the one depicted in FIG. 1,the image data processor is located in a separate unit 27.Electrocardiogram (ECG) synchronization signal generator 30 provides ECGsignals used for pulse sequence and imaging synchronization. A two orthree dimensional k-space storage array of individual data elements ink-space component processor unit 34 stores corresponding individualfrequency components comprising a magnetic resonance dataset. Thek-space array of individual data elements has a designated center andindividual data elements individually have a radius to the designatedcenter.

A magnetic field generator (comprising coils 12, 14, and 18) generates amagnetic field for use in acquiring multiple individual frequencycomponents corresponding to individual data elements in the storagearray. The individual frequency components are successively acquired inan order in which radius of respective corresponding individual dataelements increases and decreases along a substantially spiral path asthe multiple individual frequency components are sequentially acquiredduring acquisition of a magnetic resonance dataset representing amagnetic resonance image. A storage processor in the k-space componentprocessor unit 34 stores individual frequency components acquired usingthe magnetic field in corresponding individual data elements in thearray. The radius of respective corresponding individual data elementsalternately increases and decreases as multiple sequential individualfrequency components are acquired. The magnetic field acquiresindividual frequency components in an order corresponding to a sequenceof substantially adjacent individual data elements in the array andmagnetic field gradient change between successively acquired frequencycomponents which are substantially minimized.

Central control unit 26 uses information stored in an internal databaseto process the detected magnetic resonance signals in a coordinatedmanner to generate high quality images of a selected slice(s) of thebody (e.g., using the image data processor) and adjusts other parametersof system 100. The stored information comprises predetermined pulsesequence and magnetic field gradient and strength data as well as dataindicating timing, orientation and spatial volume of gradient magneticfields to be applied in imaging. Generated images are presented ondisplay 40 of the operator interface. Computer 28 of the operatorinterface includes a graphical user interface (GUI) enabling userinteraction with central control unit 26 and enables user modificationof magnetic resonance imaging signals in substantially real time.Continuing with reference to FIG. 1, display processor 37 processes themagnetic resonance signals to reconstruct one or more images forpresentation on display 40, for example. Various techniques generallyknown in the art may be used for reconstruction.

FIG. 2A provides an illustration of an image acquisition sequence 200that may be implemented on the system 100, according to some of thetechniques described herein. Briefly, in each heart-beat, multipleslices are being acquired. The suppression pulses are modified such thatthe venous suppression pulse not only suppresses the venous signal forboth slices, but also the background for the slice that is upstream forvenous flow. FIG. 2B shows the spatial location of those pulses in aschematic of vascular anatomy. A vein and artery are shown in FIG. 2B,with arrows indicating the direction of blood flow. The slices ofinterest are shown by bold-lined boxes. The result of venous andbackground suppression pulses are indicated as per the legend in FIG.2A.

The example of FIG. 2A shows an implementation for N=2 (i.e.simultaneously acquiring 2 slices). The slices being simultaneouslyimaged should be spatially as close together as permitted by the designof pulses so as to allow adequate arterial inflow to all slices withinthe same heart-beat.

The preparation pulses are modified such that the venous suppressionpulse is used to suppress venous signal for both slices and also thebackground of the slice that is upstream for venous flow. To suppressthe background of the other slice, a slice-selective saturation RF pulseis applied to the slice to set the longitudinal magnetization of tissueswithin the slice to zero is used. The pulse may rotate the magnetizationby a 90° flip angle or a 180° flip angle, although use of a 180° flipangle may provide more sensitivity to variations in heart rate comparedwith a 90° flip angle.

During the QI time, blood that was unaffected by the two suppressionpulses now flows into both slices. A spectrally selectivefat-suppression pulse is applied to attenuate signal from background fatsignal. This is followed by the SMS acquisition. The process is thenrepeated in each heartbeat, acquiring multiple slices in each heart-beatas against a single slice per heart-beat as is done in conventionalapproaches.

FIG. 3A provides an illustration of an alternative image acquisitionsequence 300, according to some embodiments. As with implementationshown in FIG. 2, during the image acquisition sequence 300, multipleslices are acquired in each heart-beat. However, each slice has itsdedicated set of two suppression pulses for background and venoussuppression. The second venous suppression pulse is applied to suppressvenous blood between slices. The venous suppression pulse of the slicethat is upstream for arterial flow (and downstream for venous flow) isvery thin, covering only the gap between the two slices. Thus, a totalof 4 suppression pulses are applied, giving more flexibility in theirdesign and spatial selectivity, at the expense of transmittingadditional radiofrequency energy which is deposited into the body beingimaged.

FIG. 3B shows the spatial location of the pulses applied in FIG. 3A in aschematic of vascular anatomy. As with the example provided in FIG. 2B,a vein and artery, with arrows indicating the direction of blood flow.The slices of interest are shown by bold-lined boxes. The result ofvenous and background suppression pulses are indicated as per the legendin FIG. 3A.

FIG. 4 shows a process 400 for using magnetic resonance angiography toproduce an image representative of the vasculature of a subject,according to some embodiments of the present invention. Starting at step405 a signal indicative of a cardiac phase of the subject is acquired,for example, using an ECG device operably coupled to the MRI system.Next, at steps 410-425, an acquisition process is performed during eachheartbeat of the subject to acquire a plurality of image slices coveringa region of interest within the subject. Briefly, the acquisitionprocess includes a sequence of preparatory pulses applied at 410-420 toa group of slices followed by a simultaneous multi-slice (SMS)acquisition of the prepared slices at step 425.

Each acquisition process may be performed following a user-selected timedelay after the R-wave of each heartbeat. The slices acquired duringeach heartbeat include an “upper” slice which is the top-most slice tobe acquired and one or more slices that are upstream for venous flow inthe region of interest. At step 410, a volume-selective venoussuppression pulse is applied to the subject to suppress (a) venoussignal from an upper slice in the region of interest; (b) venous signalfrom the upstream slices; and (c) background signal from the upstreamslices. This volume-selective venous suppression pulse may be, forexample, a tracking saturation pulse applied downstream to the upperslice and the upstream slices.

At step 415, a slice-selective background suppression pulse is appliedto the subject to suppress background signal of the upper slice. Theslice-selective background suppression pulse may apply, for example, a90 or 180 degree flip angle to the upper slice. Following a quiescenttime interval, a spectrally selective fat suppression pulse is appliedat step 420 to the upper slice and the upstream slices to attenuatesignal from background fat signal. In some embodiments, the spectrallyselective fat suppression pulse is a 90° RF pulse which rotatesmagnetizations of the upper slice and the one or more upstream slicesinto the x-y plane of the subject. In other embodiments, the spectrallyselective fat suppression pulse is a 180° RF pulse which completelyinverts longitudinal magnetization of fat in the slices. The method 400may then further include an additional step (not shown in FIG. 4) adelay is introduced to wait a predetermined inversion time prior toperforming the SMS acquisition of the slices. This predeterminedinversion time is selected such that longitudinal magnetization of fatin the slices recovers through a zero point when acquiring k-space dataduring the acquisition.

Continuing with reference to FIG. 4, at step 425, a SMS is performed toacquire k-space data covering the upper slice and the upstream slices.This acquisition may generally be performed using any technique known inthe art. For example, in some embodiments, single-shot imagingtechniques are applied at step 425. Various pulse sequences known in theart may be used in performing the acquisition. For example, in oneembodiment, a balanced steady-state free precession pulse sequence isused at step 425.

FIG. 5 illustrates an exemplary computing environment 500 within whichembodiments of the invention may be implemented. For example, thiscomputing environment 500 may be used to implement portions of theprocess 400 described above with respect to FIG. 4. In some embodiments,the computing environment 500 may be used to implement one or more ofthe components illustrated in the system 100 of FIG. 1. The computingenvironment 500 may include computer system 510, which is one example ofa computing system upon which embodiments of the invention may beimplemented. Computers and computing environments, such as computersystem 510 and computing environment 500, are known to those of skill inthe art and thus are described briefly here.

As shown in FIG. 5, the computer system 510 may include a communicationmechanism such as a bus 521 or other communication mechanism forcommunicating information within the computer system 510. The computersystem 510 further includes one or more processors 520 coupled with thebus 521 for processing the information. The processors 520 may includeone or more central processing units (CPUs), graphical processing units(GPUs), or any other processor known in the art.

The computer system 510 also includes a system memory 530 coupled to thebus 521 for storing information and instructions to be executed byprocessors 520. The system memory 530 may include computer readablestorage media in the form of volatile and/or nonvolatile memory, such asread only memory (ROM) 531 and/or random access memory (RAM) 532. Thesystem memory RAM 532 may include other dynamic storage device(s) (e.g.,dynamic RAM, static RAM, and synchronous DRAM). The system memory ROM531 may include other static storage device(s) (e.g., programmable ROM,erasable PROM, and electrically erasable PROM). In addition, the systemmemory 530 may be used for storing temporary variables or otherintermediate information during the execution of instructions by theprocessors 520. A basic input/output system (BIOS) 533 containing thebasic routines that help to transfer information between elements withincomputer system 510, such as during start-up, may be stored in ROM 531.RAM 532 may contain data and/or program modules that are immediatelyaccessible to and/or presently being operated on by the processors 520.System memory 530 may additionally include, for example, operatingsystem 534, application programs 535, other program modules 536 andprogram data 537.

The computer system 510 also includes a disk controller 540 coupled tothe bus 521 to control one or more storage devices for storinginformation and instructions, such as a hard disk 541 and a removablemedia drive 542 (e.g., floppy disk drive, compact disc drive, tapedrive, and/or solid state drive). The storage devices may be added tothe computer system 510 using an appropriate device interface (e.g., asmall computer system interface (SCSI), integrated device electronics(IDE), Universal Serial Bus (USB), or FireWire).

The computer system 510 may also include a display controller 565coupled to the bus 521 to control a display 566, such as a cathode raytube (CRT) or liquid crystal display (LCD), for displaying informationto a computer user. The computer system includes an input interface 560and one or more input devices, such as a keyboard 562 and a pointingdevice 561, for interacting with a computer user and providinginformation to the processor 520. The pointing device 561, for example,may be a mouse, a trackball, or a pointing stick for communicatingdirection information and command selections to the processor 520 andfor controlling cursor movement on the display 566. The display 566 mayprovide a touch screen interface which allows input to supplement orreplace the communication of direction information and commandselections by the pointing device 561.

The computer system 510 may perform a portion or all of the processingsteps of embodiments of the invention in response to the processors 520executing one or more sequences of one or more instructions contained ina memory, such as the system memory 530. Such instructions may be readinto the system memory 530 from another computer readable medium, suchas a hard disk 541 or a removable media drive 542. The hard disk 541 maycontain one or more datastores and data files used by embodiments of thepresent invention. Datastore contents and data files may be encrypted toimprove security. The processors 520 may also be employed in amulti-processing arrangement to execute the one or more sequences ofinstructions contained in system memory 530. In alternative embodiments,hard-wired circuitry may be used in place of or in combination withsoftware instructions. Thus, embodiments are not limited to any specificcombination of hardware circuitry and software.

As stated above, the computer system 510 may include at least onecomputer readable medium or memory for holding instructions programmedaccording to embodiments of the invention and for containing datastructures, tables, records, or other data described herein. The term“computer readable medium” as used herein refers to any medium thatparticipates in providing instructions to the processor 520 forexecution. A computer readable medium may take many forms including, butnot limited to, non-volatile media, volatile media, and transmissionmedia. Non-limiting examples of non-volatile media include opticaldisks, solid state drives, magnetic disks, and magneto-optical disks,such as hard disk 541 or removable media drive 542. Non-limitingexamples of volatile media include dynamic memory, such as system memory530. Non-limiting examples of transmission media include coaxial cables,copper wire, and fiber optics, including the wires that make up the bus521. Transmission media may also take the form of acoustic or lightwaves, such as those generated during radio wave and infrared datacommunications.

The computing environment 500 may further include the computer system510 operating in a networked environment using logical connections toone or more remote computers, such as remote computer 580. Remotecomputer 580 may be a personal computer (laptop or desktop), a mobiledevice, a server, a router, a network PC, a peer device or other commonnetwork node, and typically includes many or all of the elementsdescribed above relative to computer system 510. When used in anetworking environment, computer system 510 may include modem 572 forestablishing communications over a network 571, such as the Internet.Modem 572 may be connected to bus 521 via user network interface 570, orvia another appropriate mechanism.

Network 571 may be any network or system generally known in the art,including the Internet, an intranet, a local area network (LAN), a widearea network (WAN), a metropolitan area network (MAN), a directconnection or series of connections, a cellular telephone network, orany other network or medium capable of facilitating communicationbetween computer system 510 and other computers (e.g., remote computer580). The network 571 may be wired, wireless or a combination thereof.Wired connections may be implemented using Ethernet, Universal SerialBus (USB), RJ-11 or any other wired connection generally known in theart. Wireless connections may be implemented using Wi-Fi, WiMAX, andBluetooth, infrared, cellular networks, satellite or any other wirelessconnection methodology generally known in the art. Additionally, severalnetworks may work alone or in communication with each other tofacilitate communication in the network 571.

The embodiments of the present disclosure may be implemented with anycombination of hardware and software. In addition, the embodiments ofthe present disclosure may be included in an article of manufacture(e.g., one or more computer program products) having, for example,computer-readable, non-transitory media. The media has embodied therein,for instance, computer readable program code for providing andfacilitating the mechanisms of the embodiments of the presentdisclosure. The article of manufacture can be included as part of acomputer system or sold separately.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

An executable application, as used herein, comprises code or machinereadable instructions for conditioning the processor to implementpredetermined functions, such as those of an operating system, a contextdata acquisition system or other information processing system, forexample, in response to user command or input. An executable procedureis a segment of code or machine readable instruction, sub-routine, orother distinct section of code or portion of an executable applicationfor performing one or more particular processes. These processes mayinclude receiving input data and/or parameters, performing operations onreceived input data and/or performing functions in response to receivedinput parameters, and providing resulting output data and/or parameters.

A graphical user interface (GUI), as used herein, comprises one or moredisplay images, generated by a display processor and enabling userinteraction with a processor or other device and associated dataacquisition and processing functions. The GUI also includes anexecutable procedure or executable application. The executable procedureor executable application conditions the display processor to generatesignals representing the GUI display images. These signals are suppliedto a display device which displays the image for viewing by the user.The processor, under control of an executable procedure or executableapplication, manipulates the GUI display images in response to signalsreceived from the input devices. In this way, the user may interact withthe display image using the input devices, enabling user interactionwith the processor or other device.

The functions and process steps herein may be performed automatically orwholly or partially in response to user command. An activity (includinga step) performed automatically is performed in response to one or moreexecutable instructions or device operation without user directinitiation of the activity.

The system and processes of the figures are not exclusive. Othersystems, processes and menus may be derived in accordance with theprinciples of the invention to accomplish the same objectives. Althoughthis invention has been described with reference to particularembodiments, it is to be understood that the embodiments and variationsshown and described herein are for illustration purposes only.Modifications to the current design may be implemented by those skilledin the art, without departing from the scope of the invention. Asdescribed herein, the various systems, subsystems, agents, managers andprocesses can be implemented using hardware components, softwarecomponents, and/or combinations thereof. No claim element herein is tobe construed under the provisions of 35 U.S.C. 112, sixth paragraph,unless the element is expressly recited using the phrase “means for.”

We claim:
 1. A method for using magnetic resonance angiography toproduce an image representative of the vasculature of a subject with amagnetic resonance imaging (MRI) system, the method comprising:acquiring a signal indicative of a cardiac phase of the subject; duringeach heartbeat of the subject, acquiring a plurality of image slices ofa volume covering a region of interest within the subject using anacquisition process comprising: for each of the plurality of imageslices, applying (a) a volume-selective venous suppression pulse tosuppress venous signal downstream from venous flow into the image sliceand (b) a slice-selective background suppression pulse to suppressbackground signal of the image slice; following a quiescent timeinterval, applying a spectrally selective fat suppression pulse toattenuate signal from background fat signal in the entire volume; andperforming a simultaneous multi-slice acquisition of the plurality ofimage slices.
 2. The method of claim 1, wherein each acquisition processis performed following a user-selected time delay after the R-wave ofeach heartbeat.
 3. The method of claim 1, wherein the volume-selectivevenous suppression pulse comprises a tracking saturation pulse applieddownstream from venous flow into the image slice.
 4. The method of claim1, wherein the slice-selective background suppression pulse applies a 90degree flip angle to the image slice.
 5. The method of claim 1, whereinthe slice-selective background suppression pulse applies a 180 degreeflip angle to the image slice.
 6. The method of claim 1, wherein thespectrally selective fat suppression pulse is a 90 degree RF pulse whichrotates magnetizations of the plurality of image slices into the x-yplane of the subject.
 7. The method of claim 1, wherein the spectrallyselective fat suppression pulse is a 180 degree RF pulse whichcompletely inverts longitudinal magnetization of fat in the plurality ofimage slices and wherein the method further comprises: waiting apredetermined inversion time prior to performing the simultaneousmulti-slice acquisition of the plurality of image slices, wherein thepredetermined inversion time is selected such that longitudinalmagnetization of fat in the plurality of image slices recovers through azero point when acquiring k-space data during the simultaneousmulti-slice acquisition.
 8. The method of claim 1, wherein thesimultaneous multi-slice acquisition is performed using a single-shotpulse sequence.
 9. The method of claim 8, wherein the single-shot pulsesequence is a balanced steady-state free precession pulse sequence orspoiled gradient echo sequence.
 10. The method of claim 1, wherein theacquisition process applies all of the volume-selective venoussuppression pulses prior to applying the slice-selective backgroundsuppression pulses.